Scientists have used mtDNA as a molecular clock to trace human evolution and early migration routes. Explain why mtDNA would be more useful in this research than rRNA

MtDNA is directly passed down from the mother to her offspring, unlike the normal DNA mtDNA is not shared from the father at all as during fertilisation the Egg carries the mtDNA from the mother while the Sperm only contributes the paternal half of the DNA and no structure to the developing Zygote.